A hierarchically ordered TiO2 hemispherical particle array with hexagonal-non-close-packed tops: synthesis and stable superhydrophilicity without UV irradiation.

A hierarchical TiO(2) ordered hemispherical particle array with hexagonal-non-close-packed (hncp) tops is prepared by pulsed laser deposition (PLD) using a polystyrene colloidal monolayer as a template. Compared with conventional lithography, the route presented has the advantage of low cost for producing hncp nanostructured arrays. This hierarchical particle array exhibits excellent superhydrophilicity with a water contact angle of 0 degrees without further UV irradiation. The superhydrophilic property originates from oxygen defects or vacancies on the surface of the TiO(2) nanoparticles produced by PLD and the increased roughness of the hierarchical particle arrays. More importantly, this property is very stable for half a year and could be used in self-cleaning surfaces and microfluidic devices.